<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        const set = new Set()
        set.add(1);
        set.add(1);
        set.add("1");
        console.log(set);//Set(2) {1, '1'}
        const cities = new Map()
        cities.set(1,"北京");
        cities.set(2,"上海");
        cities.set(3,"杭州");
        cities.delete(1)
        console.log(cities);//Map(2) {2 => '上海', 3 => '杭州'}
    </script>
</body>
</html>